Stainless Steel: Characteristics, Uses and Problems

Preface

These guidelines provide general information on the characteristics and common uses of stainless steel and identifies typical problems associated with this material along with common causes of its deterioration.

References

• Gayle, Margot, Look, David, and Waite, John. Metals in America’s Historic Buildings: Uses and Preservation Treatments. Washington, DC: National Park Service, 1992.

• Zahner, L. William. Architectural Metal Surfaces. New York: Wiley 2004.

Introduction

Characteristics of Stainless Steel

• Contains iron and a minimum of 10 percent chromium.

• Marketed for its corrosion resistance, sanitary qualities and modern appearance.

• Expensive initially compared to aluminum.

• Low maintenance and replacement costs.

• More durable than most sheet metals.

• Capable of being polished using an electropolishing methods.

• Early standard finishes included hot-rolled, annealed and pickled. These methods are still used today, but appearance is slightly different.

• Thin sheets were be produced using the cold reduction process (introduced in 1947), which consists of cold-rolling of the metal.

• Gold- and bronze-plated stainless steel was also produced and used in the late 1940s.

Typical Uses

Typical historical and current uses for stainless steel include:

• Martensitic stainless steel (iron-chromium alloys containing 1 percent chromium and .35 percent carbon) was originally used for cutlery and munitions in the early 1900s.

• Ferritic stainless steel (iron-chromium alloys with a low carbon content) was used for the electric light bulb filament; also common for turbine blades in the early 1900s.

• Austenitic stainless steel (iron-chromium-nickel and iron- chromium-nickel-manganese alloys containing 18 percent chromium and 8 percent nickel) were developed between 1909 and 1912 and are commonly used as formed sheets in architectural construction.

• Precipitation-hardening stainless steel (titanium, boron or beryllium added to iron-chromium-nickel alloys as hardeners) was introduced in the late 1920s.

• Manufactured in Great Britain for cutlery, stoves, and motor cars.

• Marketed in the late 1920s and early 1930s for kitchen use, public lobbies, exterior ornament, railings, hardware, doors, light fixtures, furniture, signage and equipment.

• Notable buildings incorporating the use of stainless steel include the Chrysler Building (1930) designed by William Van Alen, and the Empire State Building (1931), designed by Shreve, Lamb and Harmon.

• Used for plaques, signs and sculptural elements as well as many extruded shapes for storefronts, trim and hardware.

• Used in curtain wall construction in the 1940s and 1950s.

• Promoted in the 1950s and 1960s for gutters, roofing, flashing and sheathing.

Natural or Inherent Problems

• Corrosion: Due to stainless steel’s sensitivity to hydrochloric acids.

• Intergranular Corrosion: Under intense heat (900 to 1500 degrees Fahrenheit), the chromium content of stainless steel is removed; the damaged area is recognizable by the presence of a blue and orange stain around the affected area; such intense heat can be produced when welding.

• Pitting: Can occur when the metal is prevented from producing the chromium oxide film that protects it; this can result from dirt build-up on the surface that keeps oxygen from reaching the surface and developing this protective film.

• Galvanic Corrosion: Stainless steel can become corrosive when comes in contact with lead, nickel, copper, copper alloys and graphite.

Vandalism or Human-Induced Problems

• Dents and Scratches: Common in high-traffic areas.

• Warping: Can be caused by thermal expansion and exposure to intense heat.